This invention generally relates to a monolithic composition comprising a water-insoluble polymer and a deliquescent material. In one embodiment, the present invention relates to a polymer blended with one or more deliquescent materials to form a deliquescent material entrained polymer. In another embodiment, the monolithic composition comprises a water-insoluble polymer, a hydrophilic agent and a deliquescent material. The monolithic composition has co-continuous interconnecting channel morphology comprising three componentsxe2x80x94component A (i.e. water-insoluble polymer), component B (i.e. hydrophilic agent) and component C (i.e. deliquescent material and super-absorbent) wherein the channels consist mainly of component B and the majority of component C. Components A and B are generally immiscible within each other. In addition, one criteria for selecting component C and components A and B may be based on component C preferential affinity for component B over component A. Another criteria for selecting component C is based on the type of deliquescent and super-absorbent material. The invention further relates to an entrained polymer that includes means by which the deliquescent material located within interior portions of the polymer structure are exposed to conditions that are exterior to the polymer body. In one embodiment, the entrained polymer of the present invention is useful in the manufacture of containers and packaging for maintaining a substantially constant relative humidity in the package or container.
There are many items that are preferably stored, shipped and/or utilized in an environment that must be controlled and/or regulated. For example, in the moisture control area, containers and/or packages having the ability to absorb excess moisture trapped therein have been recognized as desirable. One application in which moisture absorbing containers are desired is for the shipment and storage of medications whose efficacy is compromised by moisture. The initial placement of medicines into a sealed moisture free container is usually controllable. Furthermore, the container for the medicine is selected so that it has a low permeability to moisture. Therefore, the medication will normally be protected from moisture until it reaches the end user. Once the medicine is received by the customer, however, the container must be repeatedly opened and closed to access the medication. Each time the container is opened and unsealed, moisture bearing air will most likely be introduced into the container and sealed therein upon closure. Unless this moisture is controlled from the atmosphere or head space of the container, it may be detrimentally absorbed by the medication. For this reason, a desiccating unit (e.g. a sachet) is conventionally added together with the medication in the container.
Other items such as electronic components may require reduced moisture conditions for optimal performance. These components maybe sealed in containers, but excess moisture that is initially trapped therein must be removed. Furthermore, the housings may not be completely moisture tight, and moisture may be allowed to seep into the container. This moisture must also be retained away from the working components. For these reasons, it is important to include a desiccating agent within the housing for absorbing and retaining excess moisture. Because of the delicacy of many of the components that are to be protected from the moisture, it is important that the desiccant used not be of a xe2x80x9cdustingxe2x80x9d nature that may contaminate and compromise the performance of the components. Therefore, it has been recognized as advantageous to expose a desiccating agent to the interior space of such containers, while at the same time shielding the working components from actual contact with the desiccating material, including desiccant dust that may be produced therefrom.
In other instances, moisture may be released from items that have been placed in containers or sealed in packaging such as packaging wrap for shipping and/or storage. Prime examples of such items are food stuffs-that release moisture during shipping and storage. In the instance of containers that are sealed and substantially impermeable to moisture, the released moisture will remain within the container. If not controlled, this released moisture may have detrimental effects on the very item that released the moisture. It has been found that a substantial amount of moisture is released from certain food products within the first forty-eight (48) hours after manufacture and packaging. This released moisture will remain until removed or controlled. If the moisture is not controlled shortly after its release, it may cause the food to degrade into a condition that is not saleable.
The present invention discloses both a structure and a method by which a monolithic polymer is produced that is capable of maintaining a substantially constant relative humidity in a package. In one embodiment, interconnecting channels are established throughout the composition. These interconnecting channels communicate the entrained deliquescent material to the appropriate areas of the exterior of the composition in a manner that permits the desired property (e.g., moisture) to migrate from outside the shaped article to interior locations where the deliquescent material is positioned. Furthermore, in one embodiment, these interconnecting channels through which the desired property is permitted to travel are occupied by hydrophilic agents (e.g., channeling agents) that control the transmission rate into the composition. The hydrophilic agents are used as bridges from the surface of the composition inwardly to the deliquescent material positioned within the composition.